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      1 //===-- ModuleUtils.cpp - Functions to manipulate Modules -----------------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // This family of functions perform manipulations on Modules.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #include "llvm/Transforms/Utils/ModuleUtils.h"
     15 #include "llvm/IR/DerivedTypes.h"
     16 #include "llvm/IR/Function.h"
     17 #include "llvm/IR/IRBuilder.h"
     18 #include "llvm/IR/Module.h"
     19 
     20 using namespace llvm;
     21 
     22 static void appendToGlobalArray(const char *Array,
     23                                 Module &M, Function *F, int Priority) {
     24   IRBuilder<> IRB(M.getContext());
     25   FunctionType *FnTy = FunctionType::get(IRB.getVoidTy(), false);
     26   StructType *Ty = StructType::get(
     27       IRB.getInt32Ty(), PointerType::getUnqual(FnTy), NULL);
     28 
     29   Constant *RuntimeCtorInit = ConstantStruct::get(
     30       Ty, IRB.getInt32(Priority), F, NULL);
     31 
     32   // Get the current set of static global constructors and add the new ctor
     33   // to the list.
     34   SmallVector<Constant *, 16> CurrentCtors;
     35   if (GlobalVariable * GVCtor = M.getNamedGlobal(Array)) {
     36     if (Constant *Init = GVCtor->getInitializer()) {
     37       unsigned n = Init->getNumOperands();
     38       CurrentCtors.reserve(n + 1);
     39       for (unsigned i = 0; i != n; ++i)
     40         CurrentCtors.push_back(cast<Constant>(Init->getOperand(i)));
     41     }
     42     GVCtor->eraseFromParent();
     43   }
     44 
     45   CurrentCtors.push_back(RuntimeCtorInit);
     46 
     47   // Create a new initializer.
     48   ArrayType *AT = ArrayType::get(RuntimeCtorInit->getType(),
     49                                  CurrentCtors.size());
     50   Constant *NewInit = ConstantArray::get(AT, CurrentCtors);
     51 
     52   // Create the new global variable and replace all uses of
     53   // the old global variable with the new one.
     54   (void)new GlobalVariable(M, NewInit->getType(), false,
     55                            GlobalValue::AppendingLinkage, NewInit, Array);
     56 }
     57 
     58 void llvm::appendToGlobalCtors(Module &M, Function *F, int Priority) {
     59   appendToGlobalArray("llvm.global_ctors", M, F, Priority);
     60 }
     61 
     62 void llvm::appendToGlobalDtors(Module &M, Function *F, int Priority) {
     63   appendToGlobalArray("llvm.global_dtors", M, F, Priority);
     64 }
     65